Asus Z9PE-D16 - Manual (Page 57)

ASUS Z9PE-D16 Series 2-39
4. CATT LED
The CATT LED indicates that the system has experienced a fatal or catastrophic error
and cannot continue to operate.
5. Q-Code LEDs
The Q-Code LED provides you a 2-digit display that shows the system status. Refer
to the Q-Code table below for more details.